Steam Condensation Induced Waterhammer

Abstract

This is the type of waterhammer that kills people. It's initiating mechanism is much different than the image most engineers have of what causes waterhammer-- i.e. fast moving steam picking up a slug of condensate and hurling it downstream against an elbow or a valve. Condensation Induced Waterhammer can be 100 times more powerful than this type of waterhammer. Because it does not require flowing steam, it often occurs during relatively quiescent periods when operators least expect it. It's most often initiated by opening a valve, even a drain valve to remove condensate. The overpressure from an event can easily exceed 1000 psi. This is enough pressure to fracture a cast iron valve, blow out a steam gasket, or burst an accordion type expansion joint. And, in fact, failure of each of these components in separate condensation induced waterhammer accidents has resulted in operator fatalities. Operators and engineers need to understand this type of waterhammer so they can avoid procedures which can initiate it and designs which are susceptible to it.